[The morphology of microcolonies as a criterion for recognizing bacteria in the differentiation of Streptococcus...

The authors studied the diagnostic importance of the morphology of microcolonies of S. pyogenes and group B streptococci in comparison with the currently used tests for the differentiation of these two species: the bacitracin test, the hydrolysis of sodium hippurate and the CAMP test. The standard tests proved to be positive in 94-97% and microcolonies had typical morphology in 86-95.7%. The statistical indices of the diagnostic effectiveness of differential tests varied within 93.8-98.9%. The diagnostic value of the study of the morphology of colonies was characterized by the following data: the sensitivity and prognostic negative value of the study were 95% for S. pyogenes and 86-89% for group B streptococci, while its specificity and prognostic positive value were 100% due to the absence of false positive results.